Background: In the era of drug-eluting stents, although bare-metal stent (BMS) remains an option for percutaneous coronary intervention (PCI), restenosis remains the Achilles' heel of BMS implantation. A recent study demonstrated several pleiotropic anti-inflammatory effects of dextromethorphan (DXM). This study aims to evaluate the effects of DXM on the outcome of PCI with BMS implantation. Methods: In this prospective, double-blind, randomized trial, we enrolled 55 patients who underwent PCI with BMS implantation from May 2006 to February 2009. The patients were divided into DXM (60 mg once daily) and placebo groups. We compared mortality rates, myocardial infarction (MI), target lesion revascularization (TLR), restenosis, stent thrombosis, and plasma levels of high-sensitivity C-reactive protein (hs-CRP) with repeated coronary angiography 6 months after the initial procedure. Results: During the 6-month follow-up period, no events of death, MI and stent thrombosis were reported in both groups. The TLR rate was 16.7% in patients receiving DXM compared to 24% receiving a placebo (P = 0.521). The restenosis rate was 30% in patients receiving DXM as compared to 40% receiving the placebo (P = 0.571). Although nonsignificant, the percentage of hs-CRP elevation was lower in the DXM group (20%) compared to the placebo group 32%; P = 0.363). Conclusions: DXM is safe to use in patients who underwent PCI. Although DXM therapy following BMS implantation did not significantly reduce the TLR and restenosis rates, it implied a trend toward a lower TLR and restenosis and reduced inflammation in the DXM group compared to the placebo group. Nonetheless, further extensive studies are warranted to elucidate the anti-restenosis effects of DXM.